/*
 * PKCS #1 (RSA Encryption)
 * Copyright (c) 2006-2009, Jouni Malinen <j@w1.fi>
 *
 * This software may be distributed under the terms of the BSD license.
 * See README for more details.
 */

#include "wpa/includes.h"

#include "wpa/common.h"
#include "wpa2/tls/rsa.h"
#include "wpa2/tls/pkcs1.h"


static int pkcs1_generate_encryption_block(u8 block_type, size_t modlen,
        const u8* in, size_t inlen,
        u8* out, size_t* outlen)
{
    size_t ps_len;
    u8* pos;

    /*
     * PKCS #1 v1.5, 8.1:
     *
     * EB = 00 || BT || PS || 00 || D
     * BT = 00 or 01 for private-key operation; 02 for public-key operation
     * PS = k-3-||D||; at least eight octets
     * (BT=0: PS=0x00, BT=1: PS=0xff, BT=2: PS=pseudorandom non-zero)
     * k = length of modulus in octets (modlen)
     */

    if (modlen < 12 || modlen > *outlen || inlen > modlen - 11) {
        wpa_printf(MSG_DEBUG, "PKCS #1: %s - Invalid buffer "
                   "lengths (modlen=%lu outlen=%lu inlen=%lu)",
                   __func__, (unsigned long) modlen,
                   (unsigned long) *outlen,
                   (unsigned long) inlen);
        return -1;
    }

    pos = out;
    *pos++ = 0x00;
    *pos++ = block_type; /* BT */
    ps_len = modlen - inlen - 3;

    switch (block_type) {
        case 0:
            os_memset(pos, 0x00, ps_len);
            pos += ps_len;
            break;

        case 1:
            os_memset(pos, 0xff, ps_len);
            pos += ps_len;
            break;

        case 2:
            if (os_get_random(pos, ps_len) < 0) {
                wpa_printf(MSG_DEBUG, "PKCS #1: %s - Failed to get "
                           "random data for PS", __func__);
                return -1;
            }

            while (ps_len--) {
                if (*pos == 0x00) {
                    *pos = 0x01;
                }

                pos++;
            }

            break;

        default:
            wpa_printf(MSG_DEBUG, "PKCS #1: %s - Unsupported block type "
                       "%d", __func__, block_type);
            return -1;
    }

    *pos++ = 0x00;
    os_memcpy(pos, in, inlen); /* D */

    return 0;
}


int pkcs1_encrypt(int block_type, struct crypto_rsa_key* key,
                  int use_private, const u8* in, size_t inlen,
                  u8* out, size_t* outlen)
{
    size_t modlen;

    modlen = crypto_rsa_get_modulus_len(key);

    if (pkcs1_generate_encryption_block(block_type, modlen, in, inlen,
                                        out, outlen) < 0) {
        return -1;
    }

    return crypto_rsa_exptmod(out, modlen, out, outlen, key, use_private);
}


int pkcs1_v15_private_key_decrypt(struct crypto_rsa_key* key,
                                  const u8* in, size_t inlen,
                                  u8* out, size_t* outlen)
{
    int res;
    u8* pos, *end;

    res = crypto_rsa_exptmod(in, inlen, out, outlen, key, 1);

    if (res) {
        return res;
    }

    if (*outlen < 2 || out[0] != 0 || out[1] != 2) {
        return -1;
    }

    /* Skip PS (pseudorandom non-zero octets) */
    pos = out + 2;
    end = out + *outlen;

    while (*pos && pos < end) {
        pos++;
    }

    if (pos == end) {
        return -1;
    }

    pos++;

    *outlen -= pos - out;

    /* Strip PKCS #1 header */
    os_memmove(out, pos, *outlen);

    return 0;
}


int pkcs1_decrypt_public_key(struct crypto_rsa_key* key,
                             const u8* crypt, size_t crypt_len,
                             u8* plain, size_t* plain_len)
{
    size_t len;
    u8* pos;

    len = *plain_len;

    if (crypto_rsa_exptmod(crypt, crypt_len, plain, &len, key, 0) < 0) {
        return -1;
    }

    /*
     * PKCS #1 v1.5, 8.1:
     *
     * EB = 00 || BT || PS || 00 || D
     * BT = 00 or 01
     * PS = k-3-||D|| times (00 if BT=00) or (FF if BT=01)
     * k = length of modulus in octets
     */

    if (len < 3 + 8 + 16 /* min hash len */ ||
            plain[0] != 0x00 || (plain[1] != 0x00 && plain[1] != 0x01)) {
        wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature EB "
                   "structure");
        return -1;
    }

    pos = plain + 3;

    if (plain[1] == 0x00) {
        /* BT = 00 */
        if (plain[2] != 0x00) {
            wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature "
                       "PS (BT=00)");
            return -1;
        }

        while (pos + 1 < plain + len && *pos == 0x00 && pos[1] == 0x00) {
            pos++;
        }
    } else {
        /* BT = 01 */
        if (plain[2] != 0xff) {
            wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature "
                       "PS (BT=01)");
            return -1;
        }

        while (pos < plain + len && *pos == 0xff) {
            pos++;
        }
    }

    if (pos - plain - 2 < 8) {
        /* PKCS #1 v1.5, 8.1: At least eight octets long PS */
        wpa_printf(MSG_INFO, "LibTomCrypt: Too short signature "
                   "padding");
        return -1;
    }

    if (pos + 16 /* min hash len */ >= plain + len || *pos != 0x00) {
        wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature EB "
                   "structure (2)");
        return -1;
    }

    pos++;
    len -= pos - plain;

    /* Strip PKCS #1 header */
    os_memmove(plain, pos, len);
    *plain_len = len;

    return 0;
}
